Carex cephaloidea (Thin-leaf Sedge)
|Also known as:||Cluster-bracted Sedge|
|Habitat:||sun; moist to dry; rich woods, forest edges, thickets, stream banks|
|Fruiting season:||June - July|
|Plant height:||1 to 4 feet|
|Wetland Indicator Status:||GP: none MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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A cluster ½ to 1½ inches long at the top of the stem, made up of 5 to 10 round to oval spikes, the uppermost spikes tightly crowded, the lower spikes more separated but by less than twice the length of the lowest spike. The terminal spike has staminate (male) flowers at the tip and pistillate (female) flowers at the base (androgynous), with the lateral spikes usually androgynous though some may be all pistillate. At the base of the lowest spike may be a slender bract up to about ¾ inch long that does not overtop the terminal spike, but bracts are often absent altogether.
Leaves and stems:
Leaves are basal and alternate, mostly near the base, thin, mostly floppy, the largest 4 to 8 mm wide, shorter than to a little longer than the flowering stems, though vegetative shoots may be longer. Stem leaf sheaths loosely wrap the stem and are translucent whitish, cross-wrinkled (rugose), fragile and easily torn. The ligule (membrane where the leaf joins the sheath) is about as long as or slightly longer than wide. Leaves are hairless and V-shaped in cross-section when young.
The back of the sheath is longitudinally green and white striped or mottled, with green cross-veins. Bases are wrapped in a brown sheath that may become fibrous with age. Stems are erect to ascending, up to 4 mm wide at the base and much more slender above, 3-sided, very rough textured on the upper stem, elongating up to 4 feet at maturity. Plants are clump-forming and not colony-forming.
Fruit develops in late spring through early summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes each contain 6 to 20 fruits that are spreading to ascending and crowded on the stalk.
Pistillate scales are egg-shaped to nearly round, translucent white or tinged brown, with a green midrib, blunt or pointed at the tip, sometimes the midrib extending to a very short awn, and are about half as long as the perigynia. Perigynia are 3 to 4.5 mm long, 1.5 to 2.5 mm wide, green at maturity except yellowish at the base, obscurely 4 to 7-veined, narrowly winged, hairless but with minute teeth along the wing edge on the upper half, not much inflated but spongy at the base, flattened on the back side, generally lance-shaped in outline, widest near the middle tapering to a toothed beak up to 1.3 mm long. Achenes are 1.6 to 2 mm long, up to 1.7 mm wide, flattened lens-shaped, nearly round in outline, and mature to brown.
Carex cephaloidea is found primarily in deciduous woods and reaches the northwest tip of its range in Minnesota.
Carex is a large genus, with over 600 species in North America and 150+ in Minnesota alone. They are grouped into sections, the species in each group having common traits. Carex cephaloidea is in the Phaestoglochin section; some of its common traits are: clump forming, basal sheaths usually fibrous, sheath fronts cross-wrinkled (rugose), leaves hairless and V-shaped in cross-section when young, 3 to 15 stalkless spikes (rarely the lower are branched), terminal spike with staminate flowers at the tip (androgynous), lateral spikes androgynous or all pistillate, perigynia ascending to spreading and flattened on the back side, rounded and spongy at the base, beaked, the beak usually toothed, flattened lens-shaped achenes.
Carex cephaloidea is distinguished by its woodland habitat, loose sheaths cross-wrinkled on the front and green and white striped or mottled on the back, 5 to 10 round to oval spikes, often lacking bracts, all near the tip and overlapping but distinctly separated, the lowest by less than twice the length of the spike, spikes with 20 or fewer perigynia that are spreading to ascending, perigynia narrowly winged, flattened on the back side, 3 to 4.5mm long, green at maturity, and pistillate scales about half as long as the perigynia. Most similar are Carex cephalophora and Carex sparganioides, both of which may be found in a similar habitat, and Carex gravida, which is found in more open spaces. C. cephalophora has more tightly crowded spikes without any visible separation, sheaths that are tight, thickened at the tip and not cross-wrinkled, and pistillate scales are usually awned. C. gravida has pistillate scales nearly as long as the perigynia and its sheaths are not cross-wrinkled or only weakly so. C. sparganioides has spikes not all crowded at the tip, the lowest 2 to 4 separated by twice or more the length of the spike, and has 15 to 50 (average 20 or so) perigynia per spike.
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Photos by K. Chayka taken in Winona County. Photos courtesy Peter M. Dziuk taken in Fillmore and Winona counties.
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